System for identification of anatomical landmarks

ABSTRACT

A system including a processor and/or processor system can be used to identify landmarks in image data. The landmarks can be used to further identify anatomical targets. The landmarks and/or targets can be used to create a plan for a procedure, such as a surgical procedure. The processor can be used to determine the anatomical landmarks that can be used to identify anatomical targets in image data of a subject, even if the anatomical targets are indistinguishable in the image data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Ser. No.60/843,441, filed Sep. 8, 2006; U.S. Provisional Ser. No. 60/843,440,filed, Sep. 8, 2006; U.S. Provisional Ser. No. 60/843,435, filed Sep. 8,2006; and U.S. Provisional Ser. No. 60/843,434, filed Sep. 8, 2006 andis filed concurrently with U.S. patent application Ser. No. 11/584,814entitled “METHOD FOR IDENTIFICATION OF ANATOMICAL LANDMARKS”, U.S.patent application Ser. No. 11/584,813 entitled, “METHOD FOR PLANNING ASURGICAL PROCEDURE”, and U.S. patent application Ser. No. 11/584,422entitled, “SYSTEM FOR NAVIGATING A PLANNED PROCEDURE WITHIN A BODY”. Thedisclosures of the above applications are incorporated herein byreference.

FIELD

The present disclosure relates to a surgical procedure, and particularlyto a computer assisted surgical system for identification of anatomicallandmarks.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Surgical procedures are often performed by skilled individuals, such asphysicians. The physicians can perform various surgical procedures basedupon their training and past experience, augmented by study of aparticular patient. Nevertheless, various portions of a particularpatient may be difficult to examine or identify depending upon the areaof the anatomy to be examined and the positioning of the patient.

Surgical procedures where these difficulties may arise can includevarious neurosurgical procedures that affect various functions of thebrain. For example, a tumor or growth may be removed from a brain. Otherprocedures, however, may be performed to augment a portion of the brainwithout removing a portion of the brain, affecting surrounding tissue inthe brain, or without visual cues of differences between the area of thebrain to be affected and surrounding areas.

For example, certain neurological procedures can be performed thataffect “functional targets”. The functional targets can be portions ofthe brain that naturally affect or control various portions of theanatomy but are, for various reasons, damaged. These functional targetsin the brain can be stimulated through procedures such as deep brainstimulation. Functional targets, even if malfunctioning in a particularmanner, may not differ anatomically or visually from the surroundingtissues. Therefore, it is desirable to provide a system that is able todetermine the position of a functional target in the brain.

SUMMARY

A computer assisted surgical system or navigation system can be used todetermine a portion of anatomy, such as a portion in a brain, that maynot be visually distinct from surrounding tissue portions. It will beunderstood that although a system can determine a particular region of abrain, it can also be used to determine a position of other portions ofthe anatomy. In one example, various imaging techniques, such asmagnetic resonance imaging (MRI) can be used to obtain a detailed imageof the brain. A system is provided that can determine various anatomicalor functional targets based upon landmarks in the brain, plan a route ortrajectory to reach the selected anatomical targets, and determine apoint of entry to reach the anatomical target. The system can be fullyautomatic and include a processor to execute instructions to determinethe anatomical targets. The system can also be combined with manualinputs. The anatomical target can include a functional target which canbe a portion of the brain that controls a certain function of theanatomy. Although it will be understood that a similar system can beused to obtain access or determine a position of a tumor, a damagedregion of the brain, portions of the brain based upon an anatomicallandmarks, or other portions of the anatomy.

According to various embodiments a system to determine a location of aregion in an anatomy is taught. The system can include a processoroperable to execute instructions and a memory system to storeinstructions to be executed by the processor and an image data of theanatomy. A display can also be provided to display the determinedlocation of the region of the anatomy. A user input can allow a user toprovide a seed datum to the processor. The processor can executeinstructions stored in the memory system to determine the location ofthe region of the anatomy in the image data based upon the seed datum.

According to various embodiments a system to determine a location of aregion in an anatomy is taught. The system can include a processor toexecute instructions to process a image data and a memory system tostore instructions to be executed by the processor. A user input canalso be provided to identify a selected portion of the image data and adisplay can display the processed image data. The processor can processthe image data based upon the user input to determine the anatomicallandmark in the image data. The processor may further locate ananatomical target based upon a location relative to the determinedanatomical landmark.

According to various embodiments a system to determine a location of aregion in an anatomy is taught. The system can include an imaging systemthat can obtain image data of a brain of the anatomy including aplurality of slices of the brain and a processor to executeinstructions. The instructions executed by the processor can at leastone of smooth the image data, remove unneeded data from the image data,define edges in the image data, or combinations thereof. The processormay also have instructions to segment the image data to determine afirst region in the image data corresponding to a selected region in thebrain, align each of the slices of the image data based upon thedetermined first region of the image data, and determine a second regionin the image data that defines a second region of the brain. The systemcan also include a display to display at least one of the first region,the second region, or combinations thereof.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a flowchart illustrating a method of performing a surgicalprocedure;

FIG. 2 is a flowchart illustrating in greater detail a method ofdetermining an anatomical landmark;

FIGS. 3A-3C illustrate, in succession, the segmentation of image data;

FIGS. 4A-4C illustrate, in sequence, alignment of various image data;

FIG. 5 illustrates a cross-sectional view of image data with identifiedanatomical landmarks;

FIG. 6 illustrates a flowchart of a method of determining trajectoriesto reach an anatomical target;

FIG. 7 is an illustration of image data including an entry region;

FIG. 8 illustrates a system, including image data and outputs ofselected trajectories;

FIG. 9 illustrates a diagram of a surgical navigation system accordingto various embodiments;

FIG. 10 is a detailed view of the display 130 displaying an icon that isexemplary superimposed on image data;

FIG. 11 is a detailed view of a patient in a stereotactic frame;

FIG. 12 is an exemplary view of the display 130 illustrating anavigation screen.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Thoughthe following teachings relate to a method and apparatus for use with aneurosurgical procedure, this is merely exemplary and not intended tolimit the scope of the present disclosure.

Identifying various structures of an anatomy, such as portions of theneuroanatomy, can be useful for performing selected procedures on abrain, such as deep brain stimulation (DBS), ablation, tumor removal,drug delivery, gene therapy, cell delivery therapy, needle delivery,implant delivery, lead or electrode delivery, and the like. Theidentification of various brain structures can be difficult based on thelocation, size, activity, and other factors. For example, identifyingthe location of the sub-thalamic nucleus (STN) can be difficult basedupon its location within the brain and its visual similarity to the areasurrounding it. In particular, the STN may appear substantially similarto the brain tissue surrounding the STN in a patient, even if the STN orrelated portions of the brain are diseased. Nevertheless, the STN candefine a functional target that may be acted upon to achieve a preciseor selected result. It has been discovered that the STN can, however,generally be precisely located based upon its location relative toidentifiable anatomical portions of the brain. According to the presentdisclosure, the STN can be located based upon a determination oridentification of the anterior commissure (AC) and posterior commissure(PC). Thus, treatments such as DBS can be applied to the STN to treat adisease, such as Parkinson's.

With initial reference to FIG. 1, a guided procedure 18 is broadlydescribed and illustrated. The guided procedure 18 can be used forvarious types of procedures, as discussed herein, such as an imageguided or navigated procedure, a physically guided procedure (e.g., astereotactic frame), or a user or visually guided procedure. Therefore,the guided procedure 18 will be understood to be a process that allowsfor a user or a system to perform a procedure based upon identificationof various anatomical landmarks, anatomical targets, plans, ortrajectories and the like. Generally, the guided procedure 18 can beginin block 20 which is a start block. Images can be obtained of theselected portion of the anatomy in block 22. The selected portion of theanatomy can be any appropriate portion of the anatomy, such as a brainand skull. It will be understood that images can be obtained in anyappropriate manner such as, including combinations of, multi-slicecomputed tomography (MSCT), T1 weighted magnetic resonance imaging(MRI), T2 weighted MRI, high frequency ultrasound (HIFU), positronemission tomography (PET), optical coherence tomography (OCT),intra-vascular ultrasound (IVUS), ultrasound, intra-operative CT, singlephoto emission computed tomography (SPECT), planar gamma scintigraphy(PGS), or any other appropriate type of image data or combinationsthereof, including those discussed further herein. It will also beunderstood that a general or patient specific or matched atlas can beused. This can be helpful to decrease the number of patient specificimages required while maintain accuracy and quantity of image data.

The guided procedure 18, after image data is obtained in block 22, canbe used to identify anatomical landmarks in block 23 in the area in thearea where the image data was obtained. The anatomical landmarks can beidentified according to any appropriate procedures, as discussed herein.The anatomical landmarks can also be used to determine the position ofanatomical or fractional targets, as discussed in relation to block 24.The anatomical landmarks can be physically identifiable landmarks, imageidentifiable landmarks, or any appropriate landmark. The anatomicaltargets, discussed herein, can be physical targets, functional targets,or any appropriate target.

The determination of anatomical targets based on the obtained images andthe identified or determined landmarks in block 23 can be performed inblock 24. Once the targets are determined in block 24, a determinationof an appropriate trajectory to reach the target can be determined inblock 26. Then a determination of a method to perform the procedure canbe determined in block 28. Various exemplary methods of performing theprocedure can include a frameless guided procedure in block 30, astereotactic frame procedure in block 32, or a substantially openprocedure in block 34. Then the procedure can be finished in block 36including procedures such as closing the incision, removing thestereotactic frame from the patient, etc. It will be understood thatvarious other portions can be added to the guided method 18 based uponthe patient, physician choice, or the like.

Identification of landmarks 23, detection of targets in block 24 basedon images and determination of trajectory in block 26 to reach a targetcan, in its broadest sense, summarize the guided procedure 18. In otherwords, the guided procedure 18 generally includes determination oftargets on which a procedure can be performed, and a determination of atrajectory or path to reach the target based upon an entry point and thefinal target. The target can be any appropriate target (e.g., afunctional target within the brain) and the trajectory can include anyappropriate path (e.g., a straight path, a curved path, or combinationsthereof).

Further, it will be understood that the various procedures that can beperformed, such as a frameless guided procedure in block 30, astereotactic frame procedure in block 32, or a substantially openprocedure in block 34, can be performed according to any appropriatemethod and with any appropriate instruments. For example, thesubstantially frameless guided procedure can be performed with theassistance of various systems such as the AxiEM™ system provided byMedtronic Navigation, Inc. The AxiEM™ system can use trackableinstruments and trackable markers to track a location of a portion ofthe anatomy relative to an instrument. A stereotactic frame procedurecan be performed with any appropriate instrument such as the StimPilot™of Medtronic Navigation, Inc. The StimPilot™ device can use both guidedinstruments and a stereotactic frame, which can also be tracked, todetermine a location of the frame, the instrument, and a patient. Alsotracked frame systems can include those disclosed in U.S. patentapplication Ser. No. 10/651,267, now U.S. Pat. App. Pub. 2005/0049486,herein incorporated by reference. Also conventional stereotactic framescan be used, such as those discussed herein. Finally, a substantiallyopen procedure can be performed if a navigated procedure is notdesirable, available, or contraindicated. Nevertheless, it will beunderstood that the identification of landmarks, determination oftargets and the determination of trajectories in blocks 23, 24, and 26can assist a user, such as a physician, in performing an open procedure.It will also be understood that combinations of the various types ofprocedures can be performed depending upon the patient, user efficiency,and the like.

It will also be understood that the discussion herein relating to aprocedure of determining a particular portion of a brain, such as theSTN in a brain based upon the position of an AC and a PC, is merelyexemplary of a selected procedure. The guided procedure 18 can also beperformed for various reasons such as deep brain stimulation (DBS). Itwill be understood, however, that the guided procedure 18 and thevarious techniques and apparatuses described herein can be used for anyappropriate procedure. Discussion in relation to a brain and thedetermination of the STN is merely exemplary and not intended to limitthe scope of the present teachings. Further, it will be understood thatany appropriate instruments can be used to perform a procedure in thevarious exemplary systems described herein and shall not limit the scopeof appropriate systems.

As will be discussed further herein, the guided procedure 18 can be usedin any appropriate portion of a procedure. For example, a planning phasefor a procedure can be further supported and enhanced by the guidedprocedure 18 or the procedure can be performed with navigatedinstruments and the guided procedure 18 can be used to assureappropriate execution of the procedure. In particular, when planning aprocedure, a user can use the guided procedure 18 to assist inidentifying anatomical landmarks, determining an appropriate location ofvarious anatomical targets, trajectories to reach an anatomical target,and entry points. This can assist a user, such as a surgeon, ininnumerable ways, by assisting or standardizing a procedure, providingobjective results, reducing the time and costs of a procedure, reducingthe time and costs of identifying anatomical landmarks, determiningtrajectory and entry points, and determining other vital brain anatomy.The guided procedure 18 can also assist in determining an appropriatelocation of a treatment delivery device, identifying very specificportions of a selected anatomical target, or assisting in diagnosing asymptom or a disease. It will be understood that the appropriatetreatment can also be assisted by providing a system to determine anappropriate location of a selected treatment and device. Variousselected treatment planning systems can include those disclosed in U.S.patent application Ser. No. 10/651,267, now U.S. Pat. App. Pub.2005/0049486, referenced above and commonly assigned.

It will be understood that the system and procedures discussed hereincan provide assistance and standardize a surgical procedure in a numberof ways and those discussed herein are merely exemplary. The guidedprocedure 18 can be provided as a set of instructions to be executed bya processor. The processor can, based on the instructions and certaindata, identify or locate anatomical landmarks, locate targets andidentify appropriate trajectories for an instrument.

The procedure 18 again begins in block 20 and proceeds to block 22 whichincludes obtaining image data of an anatomical region. The imaging canbe of any appropriate type such as T1 weighted or T2 weighted MRIimaging. The imaging can be selected from other appropriate types ofimaging, such as computer tomography (CT), PET, SPECT, ultrasound or anyappropriate type. The imaging, such as MRI or CT imaging, can beperformed with an appropriate slice thickness such as about 1 mm, 1.5mm, 2 mm, or any appropriate thickness. The thickness and resolution ofthe imaging can be used to assist in selected procedures by increasingthe resolution and clarity of the selected anatomical regions.Nevertheless, the appropriate imaging technique can be used to createselected images, such as two-dimensional or three-dimensional images ofthe patient. The images can be 256, 512, or any appropriate pixel numbersquare or dimension. It will also be understood that the images may beany appropriate shape, for example rectangular. Also, the image data caninclude a resolution of any appropriate pixel count or pixels per areaor length. The images produced with the appropriate imaging techniquecan then be used to assist or be used in the procedure 18.

The guided procedure 18 includes the identification of landmarks inblock 23 and anatomical targets in block 24. These two blocks arefurther expanded in landmark and target (L&T) procedure 40, illustratedin FIG. 2. The L&T procedure 40 can be understood to be a subroutine ordetails of identification of landmarks in block 23 and the detection oftargets in block 24. For example, after the image data are obtained inblock 22, pre-processing of the image data can occur. The pre-processingcan include various steps, as discussed herein, to improve quality ofthe image data and remove noise or artifacts from the image data.Various pre-processing steps can include identifying generally acceptedanatomical regions or landmarks in the brain, or any portion of theanatomy, and the identification of selected targets.

The L&T process 40 can include smoothing or filtering the images inblock 42. The image pre-processing and filtering can include knownsmoothing techniques such as linear Gaussian filtering, non-linearmedian filtering, and non-linear anisotropic diffusion. Although varioussmoothing techniques can be used, it may be selected to choose anappropriate technique that allows for both smoothing while maintainingedge detection and blurring in an appropriate manner and removingirrelevant details. In one smoothing technique, the known non-linearanisotropic diffusion can smooth gray values and image data using theirgradients while not creating or destroying mass. Further, because thenon-linear anisotropic diffusion is based on fluid techniques, it isbased on the assumption that fluid is generally achieving an equilibriumstate so that there is no diffusion over an edge and the edges aregenerally perpendicular. Briefly, the non-linear anisotropic diffusionis described by equation 1:

$\begin{matrix}{\frac{\partial_{u}}{\partial_{t}} = {\nabla{\cdot \left( {D \cdot {\nabla u}} \right)}}} & (1)\end{matrix}$where D is the diffusion tensor which is a positive symmetric matrix andt denotes the diffusion time. The diffusion tensor D possesses twoorthonormal eigenvectors v₁ and v₂ described in equations 2 and 3 below:υ₁∥∇u  (2)υ₂⊥∇u  (3)

Each of the eigenvectors include corresponding eigenvalues λ₁ and λ₂described in equations 4 and 5 below:λ₁ :=g(|∇u| ²)  (4)λ₂:=1.  (5)

The eigenvectors give the main diffusion direction and the correspondingeigenvalues the strength of the diffusion in the direction of theeigenvectors. The diffusion equation 1 can be used in various formats,such as a discrete form described for various schemes. Nevertheless, anoptimized scheme can include the additive operator splitting schemedescribed in WEICKERT, J., B. M. TER HAAR ROMENY, M. A. VIERGEVER:Efficient and Reliable Schemes for Nonlinear Diffusion Filtering. IEEETransactions on Image Processing, 7(3):398-410, 1998; and WEICKERT, J.,K. J. ZUIDERVELD, B. M. TER HAAR ROMENY, W. J. NISSEN: ParallelImplementations of AOS Schemes: A Fast Way of Nonlinear DiffusionFiltering. IEEE International Conference on Image Processing, 3:396-399,1997, both incorporated herein by reference. It will be understood thatany appropriate scheme can be selected for any appropriate applicationand that the schemes described herein are merely exemplary.

Once the image data has been smoothed and filtered, the image data canbe segmented with various techniques. The segmentation of the image datacan be done for various reasons, such as with a brain scan, to determinevarious anatomical landmarks. For example, a 3-D segmentation of thethird ventricle can be obtained in block 44. The 3-D segmentation can beperformed in any appropriate manner such as with known region growingsegmentation schemes, geometric active contour models, and various otherappropriate techniques. Geometric models can be any appropriate modelsand can be based upon defining a front that evolves or changes accordingto a given curvature dependent speed function. Two different geometricmodels can be distinguished based upon the speed function, and caninclude the known level set method and the fast marching method. Theseknown methods generally create or determine a segmentation bydetermining an initial front or contour and deforming it towards theobject boundaries. A fundamental segmentation technique, however, can beany known region growing technique. Known region growing techniques canbe used according to the present teachings to include determining a 3-Dcontour of a selected region beginning with a seed point, such as avoxel, datum, portion, pixel, etc., which can also be referred to as aseed voxel herein.

The 3-D segmentation of the third ventricle in an image of the brain canbe formed according to any appropriate method such as a region growingmethod. The region growing method can begin with the seed voxel andexpand therefrom into test points (e.g. voxels, datum, or portions) andherein referred to as “voxels” based on the difference between the testvoxels touching the seed voxel and the seed voxel. In the pre-processedimage data from block 42, which are generally three-dimensional imagedata, a voxel is a three-dimensional “pixel” defined by the image data.Therefore, the test voxels that touch a seed voxel have selectedproperties that can be compared to the seed voxel. For example, eachvoxel touching the seed voxel can become a test voxel and have aproperty (e.g. an intensity, color, contrast, or brightness) compared tothe seed voxel. A distance of the property, such as the intensity) intothe test voxel touching the seed voxel can been determined, and it canbe determined how far an intensity similar to the average intensity ofthe seed voxel extends into the test voxel. If it is determined that theintensity extends a distance that is within a threshold distance intothe test voxel, the test voxel can be added to the seed voxel, thusinitiating a seed group or homogeneous region.

It will be also understood that the process can include adding a testvoxel that has an appropriate intensity and is within a selecteddistance from the seed voxel. The appropriate intensity can be within arange of the seed voxel's intensity. For example, all test voxels can beadded to the homogenous region that include a selected intensity thatare no more than, for example, five voxels from the seed voxel. It willbe understood that multiple techniques can be used to determine whethera test voxel should be added to a homogeneous region.

This process can then extend and continue until no more test voxels meetthe threshold test, thus no conforming test voxels can be found. Thenon-conforming test voxel will include an intensity that is within athreshold intensity and within a threshold distance form the seed voxel.This process creates a homogeneous region that can be relatively simpleto calculate. The homogeneous group can be one that defines the thirdventricle. It will be understood that the technique used to define anyhomogeneous group (i.e. the third ventricle) is merely exemplary.

Further, the process can be fully automatic or be assisted by a manualuser. The seed voxel can be automatically determined, manuallydetermined, or combinations thereof. For example, a user can use aninput device and a system, as discussed herein, to select a voxel as aseed voxel based on user knowledge such as relative location of thethird ventricle. The system can then use the region growing method todetermine the third ventricle. Alternatively, a system can select avoxel based on certain instructions such as intensity, location in theimage data, etc. Furthermore, a system may select several possible seedvoxels and a final choice can be made by a user. It will be understood,therefore, that the system can be substantially or completely automaticor be semi-automatic with the assistance of a user.

Briefly, as discussed above and illustrated in FIGS. 3A-3C, a smoothimage data 46 can include a seed voxel 48. After partial progress of thegrouping or homogeneity method, an initial or partial homogeneous region50 is created, as illustrated in FIG. 3B. Finally, with reference toFIG. 3C, a finalized homogeneous region 52 is created. The finalhomogeneous region can be determined when the test voxel touching thecurrent homogeneous region does not pass the threshold test. Therefore,the final homogeneous region 52 defines a homogeneous region in theimage data which can be any appropriate region, such as the thirdventricle illustrated in FIG. 3C. It will be understood that theillustration in FIG. 3C is substantially an axial view of the thirdventricle and can be viewed from different perspectives due to thethree-dimensional nature of the image data.

Returning to FIG. 2, the initially segmented image data from block 44can be aligned or rotated in block 60. The alignment or rotation of theimage data in block 60 can generally align the image data along themid-sagittal plane (MSP) or any appropriate plane, as discussed furtherherein. This can also assist in the determination of an MSP from theimage data. For example, it may be selected to align a plurality ofimages so that each of the images is substantially aligned for furthercalculation and display. It will be understood that the image data canbe aligned for any appropriate reason or may not be aligned dependingupon the selection of a user or the system. It can be selected to alignthe image data based upon further calculations or viewing by a user.

The alignment of the image data can be used for further calculations toassist in ensuring that each of the images are aligned in an appropriatemanner. The alignment may be selected for various, for example thepossibility that the images were taken with the patient in asubstantially non-fixed manner may have allowed the images to beunaligned relative to one another. The alignment of the image in block46 can ensure proper alignment of the multiple image data sets or imageslices if the patient moved during the imaging process for theproduction of the various slices.

The third ventricle, which is segmented in block 24, is generallysituated substantially near the center of the MSP and the MSP can definean appropriate symmetry of the brain. The segmentation of the thirdventricle can, therefore, be used for the alignment process. The thirdventricle can also be used to estimate the MSP for the alignmentprocess. It will be understood, however, that the alignment may not beused according to various embodiments. As discussed further herein, aline can be determined based on the determined or identified thirdventricle to assist in the alignment of the image data and/or slices.

The determination of the MSP can be based upon the segmented thirdventricle through various techniques. For example, the segmented thirdventricle can be skeletonized in each of the axial views of the imagedata. The skeletonization can include the successive thinning of thedata defining the third ventricle to determine interconnected pixelsthat are only minimally connected to generally define a line. The line,or the terminating pixels of the line, is generally equal distance fromthe edge of the homogeneous group defined during the segmentation of thethird ventricle that is segmented in block 44.

The sloping or misalignment of the MSP can then be calculated accordingto various techniques, such as the known Hough transform for linedetection. The transform can be used to determine the axial slope angleand the coronal slope angle of the line defining the skeletonized linefor the various ventricle interpretations. The whole sequence of MRIslices or images can then be rotated based upon the determined axialslope angles and coronal slope angles to substantially align thedifferent images. The rotation or the alignment can be performedaccording to any appropriate manner such as bicubic interpolation.

The MSP can then be extracted from the aligned image data based upon aninterpretation of the image data since the sagittal plane is formed ordetermined before the skeletonized lines in the aligned image data.Therefore, the MSP can be extracted from the image data to determine asubstantially symmetrical line or plane within the image data for use indetermination of various target points. The MSP is generally determinedafter the alignment of the data in block 60 so that the MSP isdetermined in block 62.

With brief reference to FIGS. 4A-4C, a skeletonized line 70 in thesmoothed image data 46 can be determined according to the processesdiscussed above. The rotation of the skeletonized line can thengenerally form an aligned skeletonized line 72 within the image data 46,as illustrated in FIG. 4B. With reference to FIG. 4C, the skeletonizedline can then be used to determine the MSP 74 in the image data 46. Itwill be understood that the description herein is merely exemplary andthat the determination of the various anatomical regions can bedetermined in any appropriate manner. For example, the skeletonized line72 can be determined relative to a plane including most of the segmentedthird ventricle in the image data slice. Also, the determination of theselected landmarks can be enhanced or made more efficient with anappropriate determination of a true axial plane thought he image data,such as with the MSP 74.

Continuing reference to FIG. 2 and the determination of targets based onthe images (e.g., the pre-processed images) can be used to determineanatomical landmarks in block 76. It will be understood that anyappropriate anatomical landmarks may be determined, for example, theidentity of the anterior commissure (AC) can be found in the images inblock 78 and the identity of the posterior commissure (PC) can be foundin the images in block 80. It is understood that determining theseparticular landmarks, the AC and the PC, are simply examples of thelandmarks that can be determined or identified in the images. The AC andthe PC can be found for selected procedures in the brain, such as deepbrain stimulation.

Identifying the AC can use various techniques. For example, the AC islocated in the brain generally immediately inferior of the column of thefornix. The AC is a bundle of nerve fibers that interconnects the twohemispheres of the brain. The bundled nerve fibers that define the AC isgenerally revealed in the image data as having high gray level intensityvalues in the image data. Therefore, after identification of the MSP,the AC can be located by finding the highest intensity pixel or pixelsthat is inferior of the MSP. Generally, the AC landmark is found in thefront contour of the third ventricle and on the same level as thebrightest pixel or the highest intensity pixel in the image data. Itwill also be understood that the AC can be found relative to the edge ofthe determined third ventricle or the edge of the commissure. Forexample, an edge of the third ventricle can be used to define a locationof the commissue and the anterior region thereof can be used to definethe AC.

The AC can also be determined or have as a seed point a region that isat an edge of the AC. In the image data the commissure includes highintensity data or bright data, as discussed above. The area adjacent tothe commissure, however, generally being the ventricle, can be dark.Thus, an area where the intensity changes can be an edge where thecommissure and the ventricle meet. The system 40 can use this as eithera starting point to determine the AC in block 78 or can use it as adetermined point for the AC, as well. It will be understood thatdetermining the appropriate AC can be performed according to any variousembodiments, including those discussed herein.

At any appropriate time, the PC can also be identified from the imagesin block 80. The PC is also a nerve bundle located in the brain thatalso crosses the mid-line of the epithalamus just dorsal to the pointwhere the cerebral aqueduct opens into the third ventricle. The PC canbe identified by its geometrical location to the cerebral aqueduct inthe image data. The cerebral aqueduct can also be determined based upon3-D segmentation of the image data to provide an additional landmark forthe determination of the PC. Various techniques can be used to segmentthe image data to determine the position of the cerebral aqueduct suchas using a histogram based method, for example, the known Otsu'sthresholding method. The thresholding method can help separate theobject, which appears dark in the image data, and the background, whichappears light. The thresholding procedure allows for a determination ofa three-dimensional boundary of a particular object. Therefore, thethresholding operation can determine the pixels in the image data thatdefine the boundary of the object, such as the cerebral aqueduct. Oncethe cerebral aqueduct can be determined, the PC can be determined due toits location relative to the cerebral aqueduct. As discussed above, thePC crosses the midline of the epithalamus just dorsal to the point wherethe cerebral aqueduct opens into the third ventricle. By determining thecerebral aqueduct relative to the third ventricle, the location of thePC can be determined in block 80.

The PC can also be determined, at least in part, by use of determiningan edge of the third ventricle and the commissure, as discussed inrelation to the AC. As discussed above the edge between the commissureand the ventricle can be used as the PC or as a starting point todetermine the PC. Also, as discussed above the edge, can be determinedautomatically by a processor analyzing the image data, manually by auser, or combinations thereof.

With reference to FIG. 5, the image of the brain 46 can be illustratedto show the various portions that are identified therein. For example,the AC can be identified as 78′ and the PC can be identified at 88′relative to the MSP 74. The determined anatomical landmarks, asillustrated in FIG. 5, can then be used to determine a location ofanatomical targets, as set out in block 24 in the guided procedure 18.The determination of anatomical targets in block 82 can be based uponthe determined landmarks. As discussed above, the landmarks can beidentified, according to various embodiments of the present teachings,from the image data obtained from a patient. The anatomical targets caninclude substantially functional targets that are relativelyindistinguishable from the surrounding structures. Therefore, thedetermination of the anatomical targets can be based upon the identifiedlocations of the identifiable anatomical target landmarks and the knownanatomical location of the target relative to the landmarks.

The anatomical targets can be any appropriate targets, for example, thesub-thalamic nucleus (STN) discussed above. The STN may be identifiedfor various purposes, such as deep brain stimulation (DBS) thereof. TheSTN can be determined relative to the anatomical landmarks by finding apoint or region a distance relative to the anatomical landmarks in theimage data. For example, the STN can be about 3.35 mm posterior, about12.3 mm lateral, and about 4.9 mm inferior of a point midway between theAC and the PC or the mid-commissural point (MCP). Therefore, afunctional target or anatomical target can be determined based upon theidentified anatomical landmarks in the image data and selecting afunctional target that is positioned in a known region relative to theanatomical landmarks, such as in the brain.

The anatomical target determined in block 82 can also be refined orassisted in determination with an instrument, such as the device 252.For example, an initial or primary target can be found or determined inblock 82. An instrument, such as a recorder or sensing device can thenbe used to assist in refining the exact location or boundaries of theanatomical target found in block 82. In other words, the recorder can beor act as an indication system. The recorder can be used to record ordetermine activity in various regions of the brain, or any anatomicalregion, to assist in refining a boundary of the anatomical target inblock 82. Thus, one will understand the determination of the anatomicaltarget can be completely automatic, partially automatic (i.e. assistedmanually by a user), or any combination thereof.

The determined location of the functional or anatomical target can thenbe used to determine a selected location for a treatment device,determine a trajectory to reach the anatomical target, or for otherpurposes as discussed in further detail herein. After the target, suchas the anatomical or functional target, has been determined or located,a determination of a trajectory to reach the target can be determined,in block 26 of the guided procedure 18. The determination of anappropriate trajectory to reach the target in block 26, is described inmore detail in a trajectory determination method 90 illustrated in aflowchart of FIG. 6.

Initially, a selection of an entry region 96 is performed in block 92.The entry region 96 can be any appropriate region of the anatomy and caninclude or be generally defined by four vertices. The four vertices candefine a two-dimensional region that can be safely used as an entrypoint for a delivery device, such as a deep brain stimulation probe.With reference to FIG. 7, the four vertices can include 94 a, 94 b, 94c, and 94 d. The region 96 defined by the four vertices 94 a-94 d cangenerally be termed the entry region 96. The entry region 96, whenperforming a procedure on the brain, can define a region of the skull orbrain that is selected for safe entry of a probe. The selected entryregion 96 can be a region known to one skilled in the art, can bedependent upon patient specific information, or combinations thereof.Nevertheless, the entry region 96 can be selected based upon knownanatomy or brain structure to substantially ensure that no critical,dangerous, or selected regions of the brain anatomy will be breached,such as various veins, sulci, and the like. The entry region for aspecific procedure, such as deep brain stimulation of the sub-thalamicnucleus, can generally be defined in the anterior region of the skull.Although any appropriate region of the skull can be used as an entryregion for an appropriate procedure.

The entry region 96 can be substantially manually determined orsubstantially automatically determined by a processor. Further, theentry region 96 can be based upon patient specific information, such asthe image data, generally accepted anatomy, or a combinations thereof.The entry region 96 can also be determined based upon a computation ofautomatic and manual determinations. For example, if the patient had aprior procedure performed in a similar area, the method and system cantake this into consideration to select an entry region 96 away from thisarea. The entry region 96 can be determined based upon many factors,such as generally accepted region of the skull or brain that is safe forentry of an instrument, patient specific information that is based uponprior procedures and particular specific anatomy of the selectedpatient, or other appropriate information. For example, when attemptingto perform DBS on the STN in the brain a region slightly anterior on theskull is generally understood to be acceptable for entry of a probe toaccess the STN. It will be understood, however, that any appropriateregion of the skull can be used to access a selected region of thebrain. Therefore, this region can be provided as the entry region 96 forthe process 90 to determine selected trajectories.

Selection of an entry region or point (block 110) can also be dependantupon the image data obtained and analyzed. For example, after thelandmarks are found in block 76 or the anatomical target is determinedin block 82 a proposed entry point or region can be determined basedupon the location of the specific target. Thus, although a generallyaccepted region or entry point can be used in the process 90 todetermine a trajectory, a proposed or determined entry point or regionbased on patient specific information, such as image data, can also beused.

Once the selection of an entry region in block 92 has been determined,the image data can be further processed or separated in block 100. Theimage separation process 100 can be any appropriate process, and may bespecifically referred to as brain separation when performing a brainspecific procedure. Generally, the image separation will allow for adetermination of boundaries of specific portions of the anatomy, such asthe boundary of the brain, to assist in determining an appropriatetrajectory to reach the anatomical targets.

The image separation in block 100 can include a subroutine 101 that caninclude various steps. A first step in the subroutine 101 can includeimage pre-processing in block 102, such as filtering and smoothing ofthe image data and illustrated in block 102 a. The image pre-processingcan include any appropriate system or methods, including the schemesdescribed above. The image pre-processing can allow for betterprocessing of the image data later by removing unneeded or unwanted dataand smoothing the data that is remaining for simplified processing. Thesubroutine 101 can also include segmentation of the brain's mass inblock 104. Segmentation of the brain mass can include segmenting theregion of the image data substantially defining the brain and removingunnecessary data, such as the skull, the optic nerves, and otherportions not relevant to selected brain structures, such as theanatomical targets, thus this can clarify the image data. Thesegmentation of the brain mass in block 104 can assist in allowing theimage data to be separated just to the area of the anatomy to beoperated on. It will be understood, however, that any appropriate regioncould be segmented and segmenting the brain mass is merely exemplary forperforming a brain specific procedure. Closing in block 106 andillustrated in block 106 a can then also be performed on the image datafor removing holes and crevices in the segmented brain mass to determinea volume which bounds and fully contains the brain mass. In other words,closing can be used to fill in an area or volume within a bound.Finally, the calculation of the outer brain boundary can be determinedin block 108 and illustrated in block 108 a. Again, it will beunderstood that any appropriate boundary can be determined anddetermining an outer brain boundary is merely exemplary for performing abrain specific procedure. Nevertheless, the brain boundary can assist indetermining various regions of the brain that can be avoided or aredesirable to be avoided in a specific procedure. The image separationsubroutine 101 can then provide a separated image to the imageseparation block 100.

After the image has been separated in block 100, determination of allpossible entry points 109 (FIG. 7) can be performed in block 110. Thedetermination of all entry points 109 in block 110 can be based upon theentry region 96 (FIG. 7) selected in block 92 and the determination ofthe location of the anatomical target 129 in block 24. The entry points109 determined in block 110 can be any possible entry point that wouldallow access to the anatomical target 129 determined in block 24. Itwill be understood that the determined entry points 109 can be basedupon a selected structure or limitation of a delivery device. Forexample, the determination of entry points 109 in block 110 can be basedupon all possible trajectories that will allow for a straight lineaccess to the anatomical target. It will be understood that the entrypoints may be augmented or different based upon the ability to move aprobe in a non-linear or leveled manner or other characteristics,including, but not limited to size, shape, or rigidity.

Determination of all possible trajectories 111 (FIG. 7) from thedetermination of entry points in block 110 to the anatomical target 129can be performed in block 112. The determination of the possibletrajectories 111 can be based upon a selected path or possible path ofan instrument, such as a deep brain stimulation probe. It will beunderstood that trajectories can be straight line, curved, orcombinations thereof and can be based upon the characteristics of theselected instruments. For example, various steerable probes or cathetersmay be used. Steerable catheters can be steered by magnetic fields,mechanical mechanisms, or other appropriate methods of mechanisms. Thepossible trajectories can be any possible trajectories 11 from all ofthe determined entry points 109 in block 110 to the determinedanatomical target 129. The determination of possible trajectories inblock 112 can be all possible trajectories or trajectories based uponselected characteristics, such as desired angles, time of calculation,and the like. Generally, determination of trajectories in block 112 canbe based simply on geometrical characteristics between the entry pointsand the anatomical targets. It will be understood that the determinationof possible trajectories in block 112 can be performed in severalselected manners. For example, as discussed herein, the image data canbe weighted and the image data can therefore include certain regionsthrough which an instrument can be passed and certain regions throughwhich an instrument cannot be passed. Therefore, the determination oftrajectories can initially take into account the weighted image data.Alternatively, the possible trajectories can include all possibletrajectories that allow a selected instrument, such as a substantiallystraighter linear probe, to pass through each of the entry points in theentry region 96 and reach the anatomical target determined in block 24.It will be understood that each of these possible trajectories mayinclude an angle, a distance, and the like, as illustrated in FIG. 7.Therefore, the determination of trajectories can include thedetermination of all possible trajectories, the initial determination ofall possible trajectories that achieve a selected result (e.g., notpassing through a selected region of the brain), or other selectedcharacteristics. Nevertheless, the possible trajectories determined inblock 112 can be further evaluated in block 116, as discussed furtherherein.

The image data can be weighted in block 114. The weighting of the imagedata can be performed at any time, but can generally weight the imagedata based upon various characteristics of the image data. For example,the various portions of the image data, such as pixels or voxels, can beweighted based upon portions of the anatomy that are to be avoided orportions of the anatomy that are harmless if passed through by aninstrument. For example, various portions, such as pixels of the imagedata, can be weighted based upon the indication that the pixel is partof a vein (i.e., shows as a bright white or bright grey area), not asulcus of the brain, not in a area that is filled with fluid, (i.e.,shows dark or has a low intensity pixel in the image data). The pixelsthat include the greatest contrast can be weighted higher while pixelswith a lower contrast can be weighted lower for determining anappropriate trajectory or for a valid weighting the trajectories inblock 116.

Different schemes can be used to weighting the image data. For example,the system can weight the image data so that no trajectory is acceptableif it passes through a vessel, a sulcus, or an area filled with fluid.Certain areas that are weighted in the image data in block 114 can beweighted in such a manner that the pixel area can absolutely not betraversed by a trajectory or can simply be weighted as better or worsethan other pixels. The schemes may also allow for a determination of abetter trajectory than another based upon the overall weight of thepixels traversed, the type of pixels traversed, etc.

The evaluation of the determined trajectories in block 116 can be basedon the image weighting in block 114, such as the weighting of thepixels, to evaluate the appropriateness of the determined trajectoriesfrom block 112. The evaluation of the determined trajectories can beused to evaluate whether a specific trajectory, which was determined inblock 112, will meet certain requirements that can be a part of theweighting process in block 114. Any trajectory that meets a thresholdcan be further evaluated based upon a comparison of a single one of thetrajectories from block 112 to any of the other determined trajectoriesfrom block 112. Once the evaluation of the determined trajectories isperformed in block 116, an output of the possible trajectories isperformed in block 118.

The output of possible trajectories in block 118 can includetrajectories that meet various criteria, such as not breaching certainweighted portions of the image data, or including a certain thresholdbased upon, or when compared to, the other trajectories. The output ofpossible trajectories in block 118 can include all trajectories and canalso include an appropriateness or optimization value. Theappropriateness value can be based on a formula for grading each of thepossible trajectories. Also, the output trajectories can include only aselected number of trajectories based upon the best or optimized or acertain number of optimized trajectories. The best trajectories can bethose that are optimized or those that have minimized a selected affecton a region of the anatomy, such as the brain. One skilled in the artwill understand that one or more plan or trajectory may have the sameoptimal affect on the selected region of the anatomy.

With reference to FIG. 8, the output of possible trajectories can be anyappropriate output, such as a human readable display 130. The humanreadable, display 130 can include a monitor that is driven by videographics portion of a system. On the display 130, the selected imagedata, such as an exemplary image data 46, is displayed. Further, anappropriate number of determined trajectories can be displayed such astrajectories 132, 134, and 136. The trajectories can also includevarious data related to the trajectories 132-136 including the length,an angle to a selected axis, a distance from the MSP, or various otherdata. The output of possible trajectories displayed on the display 130can then be used by a user, such as a physician, to determine anappropriate trajectory or to select a trajectory. Therefore, a user canmake the final determination of the appropriate trajectory that isoutput in block 118.

It will be understood that the guided procedure 18, includingdetermination of the anatomical targets in block 24 and thedetermination of trajectories in block 26 can be performed substantiallyautomatically (e.g., with a processor performing various instructions ofan algorithm), manually, or combinations thereof. For example, aprocessor (FIG. 9, reference numerals 224 a or 226) can include or beprovided with a set of instructions that, when executed, will performthe steps described in method 18, including the detailed steps in 40 and90, to determine the appropriate anatomical targets and the appropriatetrajectories to reach the targets. The processor system, described inmore detail herein, can also then output the appropriate trajectoriesfor selection by a user. The system can also be augmented by a user,where the user may perform parts of the methods or provide the seed datafor various portions of the method such as seeding the pixels or voxelsfor the segmentation. Nevertheless, the processor 224, 226 executing theinstructions can include a Pentium IV 1.6 GHz processor that cangenerally determine the anatomical targets from T1 MRI image data inabout 15-30 seconds. The image data, the instructions, and otherappropriate portions can be stored on any appropriate memory structure91 or mechanism such as a hard disk, flash memory, system RAM, orremovable storage media. The memory structure can be associated with theplanning processor 226, the work station 244, or any appropriateportion. The system can thus allow a user to substantially standardize aprocedure and reduce time of determining the various anatomicallandmarks by providing analysis of the image data by the processorsystem. It will be understood that the various portions of the methodcan be described in algorithms to determine the segmentation of thedata, the various trajectories, and the like.

Once the determination trajectory has been performed in block 26, adetermination of a method for performing the procedure can be performedin block 28. As discussed above, various types of procedures can includea frameless guided procedure in block 30, a stereotactic frame procedurein block 32, or a substantially open procedure block 34. It will also beunderstood that different procedures can be combined in an appropriatemanner to achieve a selected result. For example, a computer assistedsurgery system or a navigation system can include navigated instruments,a localizer or array, a dynamic reference frame, and other appropriateportions.

An exemplary system that can be used to automatically or substantiallyautomatically perform at least portions of the guided procedure isdiagrammatically illustrated as an image-guided navigation system 200,in FIG. 9, that can be used for various procedures with the guidedprocedure 18. The navigation system 200, including the navigationprocessor 224 and a planning processor 226 can execute instructions toperform at least portions of the guided procedure 18. The navigationsystem 200 can also be used to track the location of a device relativeto a patient 204 to assist in the implementation of the guided procedure18.

It should further be noted that the navigation system 200 may be used tonavigate or track devices including: catheters, probes, needles,guidewires, instruments, implants, deep brain stimulators, electricalleads, etc. Moreover, the device can be used in any region of the body.The navigation system 200 and various devices may be used in anyappropriate procedure, such as one that is generally minimally invasive,arthroscopic, percutaneous, stereotactic, or an open procedure. Althoughan exemplary navigation system 200 can include an imaging device 202.One skilled in the art will understand that the discussion of theimaging device 202 is merely for clarity of the present discussion andany appropriate imaging system, navigation system, patient specificdata, and non-patient specific data can be used.

The navigation system 200 can include the optional imaging device 202that is used to acquire pre-, intra-, or post-operative or real-timeimage data of a patient 204. The image data acquired with the imagingdevice 204 can be used by the procedure 18 to assist in determining theanatomical targets and the trajectories. The illustrated imaging device202 can be, for example, a fluoroscopic x-ray imaging device that may beconfigured as a C-arm 206 having an x-ray source 208, an x-ray receivingsection 210, an optional calibration and tracking target 212 andoptional radiation sensors 214. Image data may also be acquired usingother imaging devices, such as those discussed above and herein. Anexample of a fluoroscopic C-arm x-ray device that may be used as theoptional imaging device 202 is the “Series 9600 Mobile Digital ImagingSystem,” from OEC Medical Systems, Inc., of Salt Lake City, Utah. Otherexemplary fluoroscopes include bi-plane fluoroscopic systems, ceilingfluoroscopic systems, cath-lab fluoroscopic systems, fixed C-armfluoroscopic systems, isocentric C-arm fluoroscopic systems, 3Dfluoroscopic systems, etc.

The calibration and tracking target 212 can include calibration markers(not illustrated) to calibrate the imaging system 262 as is generallyknown. An optional imaging device controller 218 may control the imagingdevice 202, such as the C-arm 206, can capture the x-ray images receivedat the receiving section 210 and store the images for later use. Thecontroller 218 may also be separate from the C-arm 206 and/or controlthe rotation of the C-arm 206. For example, the C-arm 206 can move inthe direction of arrow 220 or rotate about a longitudinal axis 204 a ofthe patient 204, allowing anterior or lateral views of the patient 204to be imaged. Each of these movements involves rotation about amechanical axis 222 of the C-arm 206.

In operation, the C-arm 206 generates x-rays from the x-ray source 208that propagate through the patient 204 and calibration and/or trackingtarget 212, into the x-ray receiving section 210. It will be understoodthat the tracking target need not include a calibration portion. Thereceiving section 210 generates image data representing the intensitiesof the received x-rays. Typically, the receiving section 210 includes animage intensifier that first converts the x-rays to visible light and acharge coupled device (CCD) video camera that converts the visible lightinto digital image data. Receiving section 210 may also be a digitaldevice that converts x-rays directly to digital image data for formingimages, thus potentially avoiding distortion introduced by firstconverting to visible light. With this type of digital C-arm, which isgenerally a flat panel device, the optional calibration and/or trackingtarget 212 and the calibration process discussed below may beeliminated. Also, the calibration process may be eliminated or not usedat all for various procedures. Alternatively, the imaging device 202 mayonly take a single image with the calibration and tracking target 212 inplace. Thereafter, the calibration and tracking target 212 may beremoved from the line-of-sight of the imaging device 202.

Two dimensional fluoroscopic images that may be taken by the imagingdevice 202 are captured and stored in the C-arm controller 218. Multipletwo-dimensional images taken by the imaging device 202 may also becaptured and assembled to provide a larger view or image of a wholeregion of a patient, as opposed to being directed to only a portion of aregion of the patient. For example, multiple image data of a patient'shead may be appended together to provide a full view or complete set ofimage data of the head that can be later used. The multiple images, suchas multiple 2D images, can be stitched together to form a larger view in2D or can be reconstructed to create a 3D dataset of a volume. Otherimaging techniques such as T1 or T2 weighted MRI can be used toaccumulate multiple slices of a patient's head to form athree-dimensional model at the patient's head and brain to determinelocation of anatomical targets.

The image data can then be forwarded from the C-arm controller 218 to anavigation computer and/or processor 224 having a display 225 and a userinterface 227. The navigation processor 224, display 225, and user inputinterface 227 can be part of a work station 229. The navigationprocessor 224 can include a planning processor, as discussed herein, ora separate planning processor system 226 can be included. The planningprocessor system 226 can also include a display 228 and a user input230. It will also be understood that the image data is not necessarilyfirst retained in the controller 218, but may be directly transmitted tothe workstation 229 or the planning processor system 226.

The work station 229 or optimization processor 228 provides facilitiesfor displaying the image data as an image on the displays 226 or 228,saving, digitally manipulating, or printing a hard copy image of thereceived image data. The user interface 230, which may one or acombination of be a keyboard, mouse, touch pen, touch screen or othersuitable device, allows a physician or user to provide inputs to controlthe imaging device 202, via the C-arm controller 218, or adjust thedisplay settings of the display 225.

When the x-ray source 208 generates the x-rays that propagate to thex-ray receiving section 210, the radiation sensors 214 sense thepresence of radiation, which is forwarded to the C-arm controller 218,to identify whether or not the imaging device 202 is actively imaging.This information is also transmitted to a coil array controller 232,further discussed herein, that can be a part of the workstation 229. Forexample, the array controller 232 can be controlled by the navigationprocessor 224. Alternatively, a person or physician may manuallyindicate when the imaging device 202 is actively imaging or thisfunction can be built into the x-ray source 208, x-ray receiving section210, or the control computer 218.

While the optional imaging device 202 is shown in FIG. 9, any otheralternative 2D, 3D or 4D imaging modality may also be used. For example,any 2D, 3D or 4D imaging device, such as isocentric fluoroscopy,bi-plane fluoroscopy, ultrasound, computed tomography (CT), multi-slicecomputed tomography (MSCT), T1 weighted magnetic resonance imaging(MRI), T2 weighted MRI, high frequency ultrasound (HIFU), positronemission tomography (PET), optical coherence tomography (OCT),intra-vascular ultrasound (IVUS), ultrasound, intra-operative CT, singlephoto emission computed tomography (SPECT), or planar gamma scintigraphy(PGS) may also be used to acquire 2D, 3D or 4D pre- or post-operativeand/or real-time images or image data of the patient 204. The images mayalso be obtained and displayed in two, three or four dimensions. In moreadvanced forms, four-dimensional surface rendering regions of the bodymay also be achieved by incorporating patient data or other data from anatlas or anatomical model map or from pre-operative image data capturedby MRI, CT, or echocardiography modalities. A more detailed discussionon optical coherence tomography (OCT), is set forth in U.S. Pat. No.5,740,808, issued Apr. 21, 1998, entitled “Systems And Methods ForGuiding Diagnostic Or Therapeutic Devices In Interior Tissue Regions”which is hereby incorporated by reference.

Image datasets from hybrid modalities, such as positron emissiontomography (PET) combined with CT, or single photon emission computertomography (SPECT) combined with CT, can also provide functional imagedata superimposed onto anatomical data to be used to confidently reachtarget sites within the patient 204. It should further be noted that theoptional imaging device 202, as shown in FIG. 10, provides a virtualbi-plane image using a single-head C-arm fluoroscope as the optionalimaging device 202 by simply rotating the C-arm 206 about at least twoplanes, which could be orthogonal planes to generate two-dimensionalimages that can be converted to three-dimensional volumetric images. Byacquiring images in more than one plane, an icon representing thelocation of an impactor, stylet, reamer driver, taps, drill, deep brainstimulators, electrical leads, needles, implants, probes, or otherinstrument, introduced and advanced in the patient 204, may besuperimposed in more than one view on display 225 or 228 allowingsimulated bi-plane or even multi-plane views, including two andthree-dimensional views.

These types of imaging modalities may provide certain distinct benefitsfor their use. For example, magnetic resonance imaging (MRI) isgenerally performed pre-operatively using a non-ionizing field. Thistype of imaging provides very good tissue visualization inthree-dimensional form and also provides anatomy and functionalinformation from the imaging. MRI imaging data is generally registeredand compensated for motion correction using dynamic reference frames(DRF) discussed further herein. Also, different types of MRI techniquescan be used to more clearly illustrate different portions of theanatomy. As discussed above, T1 weighted MRI images may be used todisplay selected anatomical regions in the brain.

With continuing reference to FIG. 9, the navigation system 200 canfurther include an electromagnetic navigation or tracking system 244that includes a localizer, such as a transmitter coil array 246, a coilarray controller 248, a navigation probe interface 272, a device 252(e.g. catheter, needle, or instruments, as discussed herein) and adynamic reference frame 254. The dynamic reference frame 254 can includea dynamic reference frame member or holder 256 and a removable trackingsensor 258. Alternatively, the dynamic reference frame 254 can include atracking sensor that is formed integrally with the dynamic referenceframe member 256. One skilled in the art will understand that thetracking sensor 258 can be any appropriate device that can be anemitter, a receiver, a reflector, a sensor to sense a field, or anyother appropriate device that can be tracked by a tracking systemincluding a localizer.

The device 252 can be any appropriate device, for example and referredto herein as a catheter. Other appropriate devices can be used todelivery a therapy to a region of the anatomy or to record informationfrom a region of the anatomy. For example, a recording device can beplaced in the cranium of the patient 204 to record electrical activityof a selected region of the brain for analysis and treatment options.Thus, it will be understood that the device 252 can be selected to beany appropriate device, and a stimulator, catheter, probe, etc. aremerely exemplary.

The transmitter coil array 246 may also be supplemented or replaced witha mobile localizer 267. The mobile localizer 267 may be one such as thatdescribed in U.S. patent application Ser. No. 10/941,782, filed Sep. 15,2004, now U.S. Pat. App. Pub. No. 2005/0085720, and entitled “METHOD ANDAPPARATUS FOR SURGICAL NAVIGATION”, herein incorporated by reference. Asis understood the localizer array can transmit signals that are receivedby the dynamic reference frame 254, and a tracking sensors 260. Thedynamic reference frame 254 and the tracking sensors 260 can thentransmit signals based upon the received signals from the array.

It will be understood that the tracking system may be any appropriatetracking system and can include an optical tracking system with anoptical localizer 264, illustrated in phantom. Optical tracking systemscan include the StealthStation® TRIA™ and StimPilot™, andelectromagnetic systems can include the AxiEM™, all sold by MedtronicNavigation of Louisville, Colo. Other tracking systems include acoustic,radiation, radar, infrared, laser, accelerometer, etc. The opticallocalizer 264 can transmit and receive, or combinations thereof. Anoptical tracking sensor 266 can be interconnected with the device 252,or other portions such as the dynamic reference frame 254. As isgenerally known the tracking sensor 266 can reflect or transmit anoptical signal to the optical localizer 264 that can be used in thenavigation system 200 to navigate or track various elements.

Further included in the navigation system 200 may be an isolator circuitor assembly 270. The isolator assembly 270 may be included in atransmission line to interrupt a line carrying a signal or a voltage toa navigation device interface 272. Alternatively, the isolator circuitincluded in the isolator assembly 270 may be included in the navigationdevice interface 272, the device 252, the dynamic reference frame 254,the transmission lines coupling the devices, or any other appropriatelocation. The isolator assembly 270 is operable to isolate the patientfrom any of the instruments or portions that are in contact with thepatient 204 should an undesirable electrical surge or voltage takeplace.

It should further be noted that the entire tracking system 244 or partsof the tracking system 244 may be incorporated into the imaging device202, including the work station 229 and radiation sensors 214.Incorporating the tracking system 244 may provide an integrated imagingand tracking system. Any combination of these components may also beincorporated into the imaging system 202, which can include anappropriate imaging device.

The transmitter coil array 266 is shown attached to the receivingsection 210 of the C-arm 206. It should be noted, however, that thetransmitter coil array 266 may also be positioned at any other locationas well. For example, the transmitter coil array 266 may be positionedat the x-ray source 208, within or atop an operating room (OR) table 276positioned below the patient 204, on siderails associated with the ORtable 276, or positioned on the patient 204 in proximity to the regionbeing navigated, such as on the patient's chest. The coil array is usedin an electromagnet tracking system as the localizer therefore. It isunderstood by one skilled in the art that any appropriate localizer maybe used. The transmitter coil array 266 may also be positioned in theitems being navigated, further discussed herein. The transmitter coilarray 266 can include a plurality of coils that are each operable togenerate distinct electromagnetic fields into the navigation region ofthe patient 204, which is sometimes referred to as patient space.Representative electromagnetic systems are set forth in U.S. Pat. No.5,913,820, entitled “Position Location System,” issued Jun. 22, 1999 andU.S. Pat. No. 5,592,939, entitled “Method and System for Navigating aCatheter Probe,” issued Jan. 14, 1997, each of which are herebyincorporated by reference.

The transmitter coil array 266 is controlled or driven by the coil arraycontroller 232. The coil array controller 232 drives each coil in thetransmitter coil array 266 in a time division multiplex or a frequencydivision multiplex manner. In this regard, each coil may be drivenseparately at a distinct time or all of the coils may be drivensimultaneously with each being driven by a different frequency. Upondriving the coils in the transmitter coil array 266 with the coil arraycontroller 232, electromagnetic fields are generated within the patient204 in the area where the medical procedure is being performed, which isagain sometimes referred to as patient space. The electromagnetic fieldsgenerated in the patient space induce currents in a sensor 258positioned on or in the device 252. These induced signals from thedevice 252 are delivered to the navigation device interface 272 throughthe isolation assembly 270 and subsequently forwarded to the coil arraycontroller 232. The navigation device interface 272 may provide all thenecessary electrical isolation for the navigation system 200.Alternatively, the electrical isolation may also be provided in theisolator assembly 270. Nevertheless, the isolator assembly 270 may beincluded in the navigation device interface 272 or may be integratedinto the device 252, and any other appropriate location. The navigationdevice interface 272 can also include amplifiers, filters and buffers todirectly interface with the sensors 258 in the device 252.Alternatively, the device 252, or any other appropriate portion, mayemploy a wireless communications channel, such as that disclosed in U.S.Pat. No. 6,474,341, entitled “Surgical Communication Power System,”issued Nov. 5, 2002, herein incorporated by reference, as opposed tobeing coupled directly to the navigation device interface 272.

When the navigation system 200 uses an EM based tracking system, variousportions of the navigation system 200, such as the device 252, thedynamic reference frame (DRF) 254, the device 252, are equipped with atleast one, and generally multiple, EM tracking sensors 260, that mayalso be referred to as localization sensors. The EM tracking sensor 260can include one or more coils that are operable with the EM localizerarray 266 or 267. An alternative sensor may include an optical sensor,such as the optical sensor 258 a, and may be used in addition to or inplace of the electromagnetic sensor 258. The optical sensor may workwith the optional optical localizer 264. One skilled in the art willunderstand, however, that any appropriate tracking sensor can be used inthe navigation system 200. An additional representative alternativelocalization and tracking system is set forth in U.S. Pat. No.5,983,126, entitled “Catheter Location System and Method,” issued Nov.9, 1999, which is hereby incorporated by reference. Alternatively, thelocalization system may be a hybrid system that includes components fromvarious systems.

The EM tracking sensor 258 on the device 252 can be in a handle orinserter that interconnects with an attachment and may assist in placingan implant or in driving a portion. The device 252 can include agraspable or manipulable portion at a proximal end and the trackingsensor 258 may be fixed near the manipulable portion of the device 252or at a distal working end, as discussed herein. The tracking sensor 258can include an electromagnetic sensor to sense the electromagnetic fieldgenerated by the transmitter coil array 266 that can induce a current inthe electromagnetic sensor 258.

The dynamic reference frame 254 of the tracking system 244 is alsocoupled to the navigation device interface 272 to forward theinformation to the coil array controller 232. The dynamic referenceframe 254, according to various embodiments, may include a smallmagnetic field detector. The dynamic reference frame 254 may be fixed tothe patient 204 adjacent to the region being navigated so that anymovement of the patient 204 is detected as relative motion between thetransmitter coil array 266 and the dynamic reference frame 254. Thedynamic reference frame 254 can be interconnected with the patient inany appropriate manner, including those discussed herein. This relativemotion is forwarded to the coil array controller 232, which updatesregistration correlation and maintains accurate navigation, furtherdiscussed herein. The dynamic reference frame 254 may be any appropriatetracking sensor used as the dynamic reference frame 254 in thenavigation system 200. Therefore the dynamic reference frame 254 mayalso be optical, acoustic, etc. If the dynamic reference frame 254 iselectromagnetic it can be configured as a pair of orthogonally orientedcoils, each having the same center or may be configured in any othernon-coaxial or co-axial coil configurations.

The dynamic reference frame 254 may be affixed externally to the patient204, adjacent to the region of navigation, such as on the patient'scranium, etc., as shown in FIG. 9. The dynamic reference frame 254 canbe affixed to the patient's skin, by way of a selected adhesive patchand/or a tensioning system. The dynamic reference frame 254 may also beremovably attachable to a fiducial marker 280. The fiducial markers canbe anatomical landmarks or members attached or positioned on thepatient's 204 body. The dynamic reference frame 254 can also beconnected to a bone portion of the anatomy. The bone portion can beadjacent, the area of the procedure, the bone of the procedure, or anyappropriate bone portion.

Briefly, the navigation system 200 operates as follows. The navigationsystem 200 creates a translation map between all points in the imagedata or image space and the corresponding points in the patient'sanatomy in patient space. After this map is established, the image spaceand patient space are registered. In other words, registration is theprocess of determining how to correlate a position in image space with acorresponding point in real or patient space. This can also be used toillustrate a position of the device relative to the proposed trajectoryand/or the determined anatomical target. The work station 229 incombination with the coil array controller 232 and the C-arm controller218 identify the corresponding point on the pre-acquired image or atlasmodel relative to the tracked device 252 and display the position ondisplay 225. This identification is known as navigation or localization.An icon representing the localized point or instruments is shown on thedisplay 225 within several two-dimensional image planes, as well as onthree and four dimensional images and models.

To register the patient 204, a physician or user 282 may use pointregistration by selecting and storing particular points from thepre-acquired images and then touching the corresponding points on thepatient's anatomy with a pointer probe or any appropriate trackeddevice, such as the device 252. The navigation system 200 analyzes therelationship between the two sets of points that are selected andcomputes a match, which allows for a determination of a correlation ofevery point in the image data or image space with its correspondingpoint on the patient's anatomy or the patient space.

The points that are selected to perform registration or form atranslation map are the fiducial markers 280, such as anatomical orartificial landmarks. Again, the fiducial markers 280 are identifiableon the images and identifiable and accessible on the patient 204. Thefiducial markers 280 can be artificial landmarks that are positioned onthe patient 204 or anatomical landmarks that can be easily identified inthe image data. The artificial fiducial markers 280, can also form partof the dynamic reference frame 254, such as those disclosed in U.S. Pat.No. 6,381,485, entitled “Registration of Human Anatomy Integrated forElectromagnetic Localization,” issued Apr. 30, 2002, herein incorporatedby reference. It will be understood that the “X” illustrated in FIG. 9can merely indicate a position of a fiducial marker 280 rather thanbeing the fiducial marker 280.

The system 200 may also perform registration using anatomic surfaceinformation or path information as is known in the art (and may bereferred to as auto-registration). The system 200 may also perform 2D to3D registration by utilizing the acquired 2D images to register 3Dvolume images by use of contour algorithms, point algorithms or densitycomparison algorithms, as is known in the art. An exemplary 2D to 3Dregistration procedure, is set forth in U.S. Ser. No. 10/644,680, filedon Aug. 20, 2003, now U.S. Pat. App. Pub. No. 2004-0215071, entitled“Method and Apparatus for Performing 2D to 3D Registration”, herebyincorporated by reference.

In order to maintain registration accuracy, the navigation system 200continuously can track the position of the patient 204 duringregistration and navigation with the dynamic reference frame 254. Thisis because the patient 204, dynamic reference frame 254, and transmittercoil array 266 may all move during the procedure, even when thismovement is not desired. Alternatively the patient 204 may be heldimmobile once the registration has occurred, such as with a head frame.Therefore, if the navigation system 200 did not track the position ofthe patient 204 or area of the anatomy, any patient movement after imageacquisition would result in inaccurate navigation within that image. Thedynamic reference frame 254 allows the tracking system 244 to track theanatomy and can assist in registration. Because the dynamic referenceframe 254 is rigidly fixed to the patient 204, any movement of theanatomy or the transmitter coil array 266 is detected as the relativemotion between the transmitter coil array 266 and the dynamic referenceframe 254. This relative motion is communicated to the coil arraycontroller 232, via the navigation probe interface 272, which updatesthe registration correlation to thereby maintain accurate navigation.

The dynamic reference frame 254 can be affixed to any appropriateportion of the patient 204, and can be used to register the patient tothe image data, as discussed above. For example, when a procedure isbeing performed relative to a cranium 288, the dynamic reference frame254 can be interconnected with the cranium 288. The dynamic referenceframe 254 can be interconnected with the cranium 288 in any appropriatemanner, such as those discussed herein according to various embodiments.

To enable navigation, registration must be had and the navigation system200 must be able to detect both the position of the patient's anatomyand the position of the device 252 or attachment member (e.g. trackingsensor 258) attached to the device 252. Knowing the location of thesetwo items allows the navigation system 200 to compute and display theposition of the device 252 or any portion thereof in relation to thepatient 204. The tracking system 244 is employed to track the device 252and the anatomy simultaneously.

The tracking system 244, if it is using an electromagnetic trackingassembly, essentially works by positioning the transmitter coil array266 adjacent to the patient space to generate a low-energy magneticfield generally referred to as a navigation field. Because every pointin the navigation field or patient space is associated with a uniquefield strength, the electromagnetic tracking system 244 can determinethe position of the device 252 by measuring the field strength at thetracking sensor 258 location. The dynamic reference frame 254 is fixedto the patient 204 to identify the location of the patient in thenavigation field. The electromagnetic tracking system 244 continuouslyrecomputes the relative position of the dynamic reference frame 254 andthe device 252 during localization and relates this spatial informationto patient registration data to enable image guidance of the device 252within and/or relative to the patient 204.

To obtain a maximum reference it can be selected to fix the dynamicreference frame 254 in each of at least 6 degrees of freedom. Thus, thedynamic reference frame 254 or any of the tracking sensors 258 can befixed relative to axial motion X, translational motion Y, rotationalmotion Z, yaw, pitch, and roll relative to the portion of the patient204 to which it is attached. Any appropriate coordinate system can beused to describe the various degrees of freedom. Fixing the dynamicreference frame relative to the patient 204 in this manner can assist inmaintaining maximum accuracy of the navigation system 200.

In addition the dynamic reference frame 254 can be affixed to thepatient in such a manner that the tracking sensor portion thereof isimmovable relative to the area of interest, such as the cranium 288. Ahead band may form a part of the dynamic reference frame 254. Further, astereotactic frame, as generally known in the art, can be attached tothe head band. Such systems for tracking and performing procedures aredisclosed in U.S. patent application Ser. No. 10/651,267, filed on Aug.28, 2003, now U.S. Pat. App. Pub. 2005/0049486, and incorporated hereinby reference.

Although the navigation system 244, discussed above, can be provided ina plurality of ways and with a plurality of mechanisms it can be used totrack the device 252. As discussed above the device can be a catheter252 and can be any appropriate catheter and can include a trackingsensor such as the tracking sensor 258. Briefly, it will be understoodthat the catheter 252 can represent any appropriate instrument such as adeep brain stimulator, a needle, a probe, a guidewire, etc. The trackingsensor 258 included in the catheter 252 can be any appropriate trackingsensor and can be formed in any appropriate manner such as the cathetersdescribed in pending U.S. patent application Ser. No. 11/241,837, filedon Sep. 30, 2005, now U.S. Pat. App. Pub. No. 2006/0084867, incorporatedherein by reference. The catheter 252 can include the tracking sensors258 at any appropriate position, such as near a distal end of thecatheter 252. By positioning the tracking sensors 258 near the distalend of the catheter 252 knowing or determining a precise location of thedistal end can be easily done. Determining a position of the distal endof the catheter 252 can be used to achieve various results, such asdetermining a precise position of the distal end of the catheter 252, aprecise movement of the distal end of the catheter 252, or otherappropriate purposes. It will be understood that knowing a position andmoving the catheter 252 in a precise manner can be useful for variouspurposes, including those discussed further herein. Likewise, thecatheter 252 can be directable according to various mechanisms and suchas directing or pulling wires, directing or pulling signals, or anyappropriate mechanism generally known in the art.

The device 252 can be used for various mechanisms and methods, such asdelivering a material to a selected portion of the patient 204, such aswithin the cranium 288. The material can be any appropriate materialsuch as a bioactive material, a pharmacological material, a contrastagent, or any appropriate material. As discussed further herein, thecatheter device 252 can be precisely positioned via the navigationsystem 200 and otherwise used to achieve a protocol for positioning thematerial relative to the patient 204 in any appropriate manner, such aswithin the cranium 288. The device 252 may also include a brain probe toperform deep brain stimulation. The device 252 could then be tracked tonavigate it along the determined trajectory to stimulate an anatomicaltarget such as the STN.

The navigation system 200, or any appropriate navigation system, can beused with various frames that can assist in performing a procedure.Portions of the frame can be navigated or tracked with the navigationsystem 200 to assist in guiding navigated instruments. Various framescan include those described in U.S. patent application Ser. No.10/651,267, now U.S. Pat. App. Pub. 2005/0049486, referenced above. Thestereotactic frames can allow for registration of patient space to apre-acquired image to insure that the planned trajectory is achievedrelative to the patient. In addition to various guided stereotacticframes, stereotactic frames can also include non-navigated frames orframes that can be used for determination of entry points, trajectories,and the like. Also, various stereotactic frames, such as the CRW offeredby Radionics, Inc. may be utilized with the above-described guidedprocedure 18.

As briefly described above, the guided procedure 18 can be used todetermine any appropriate type of procedure such as the frameless guidedprocedure in block 30, a stereotactic frame procedure in block 32, or anopen procedure in block 34. These types of procedures can still takeadvantage of the guided procedure 18 substantially defined or describedin blocks 23, 24, and 26. For example, the anatomical landmarks,anatomical targets, and planned trajectories can all be determined andthen a procedure can be performed in any appropriate manner.

For example, with reference to block 30 of the guided procedure 18, asubstantially frameless (i.e., without the use of a stereotactic frame)procedure can be performed. With brief reference to FIG. 8, a user, suchas a physician, can determine that trajectory 132 is the mostappropriate trajectory based upon the information relating to trajectory132, the physician's experience, or any other appropriate reason. Withreference to FIGS. 9 and 10, a user can view on a display 130, 228, or225, the image data 46 of a selected region of the patient, such as thebrain or cranium thereof. The display 130 can include an icon 132 a,which can include a dashed line showing the proposed trajectory for theprocedure. The user 282 can then guide the instrument 252 using thenavigation elements, such as the tracking sensor 262 interconnected withthe instruments 252 to allow the navigation system 200 to illustrate onthe display 130 the path of the instrument 252.

Once the trajectory has been determined, including the entry point, thephysician 282 can move the tracked instrument 252 relative to thepatient 204, which has been registered to the image space as discussedabove, to move the instruments 252 relative to the patient 204 and thedetermined entry point. It will be understood that the instrument 252can be a plurality of instruments, such as a burr to form an entry port,a deep brain stimulation probe, or electrode to perform a procedure, orany other appropriate instrument that may be interchanged for variouspurposes. An icon, such as an arrow or a separate color, or a dark orsolid line 132 b can be illustrated relative to the image data 46 toillustrate the position of the instrument 252 relative to the image data46 which correlates to the position of the instrument 252 relative tothe patient 204.

As the physician 282 continues to move the instrument 252 relative tothe patient, the icon 132 b representing the position of the instrument252 on the image data 46 can be shown to progress relative to theplanned trajectory 132 a which can also be illustrated on the image data46. It will be understood that the icons 132 a, 132 b can besuperimposed on the image data or the icons 132 a, 132 b can bedisplayed alone on the display 130 when performing an imagelessprocedure. It will be understood that the instrument 252 can be trackedwith the icon 132 b illustrating the position of the instrument 252relative to the planned trajectory 132 a. Various warnings can beprovided, such as audible warnings, screen warnings, or the like toindicate when the instrument 252 is no longer on the planned trajectory132 a. Further, the navigation system 200, or a portion thereof, canprovide various signals, such as audible or visible signals, when theinstrument 252 reaches the selected anatomical target 129. Once theinstrument 252 has reached the anatomical target 129, as illustrated bythe icon 132 b on the display 130, the procedure can proceed to the nextstep, such as the positioning of a probe, the stimulation of a portionof the brain, or any appropriate procedure.

Although the procedure can proceed with a frameless scatter procedure inblock 30, the procedure can also proceed relative or with a stereotacticframe as in block 32. Various stereotactic frames can include astereotactic frame 300 illustrated in FIG. 11. The stereotactic frame300 is generally described in U.S. patent application Ser. No.10/651,267, now U.S. Pat. App. Pub. 2005/0049486, incorporated herein byreference. The stereotactic frame 300 will not be described in detailhere, save for in relation to the guided procedure 18. Generally, thestereotactic frame 300 can include tracking sensors 262 a-g. The varioustracking sensors 262 a-g can be provided to track the various portionsof the stereotactic frame 300 relative to the patient 204. One or moreof the tracking sensors 262 a-g can be provided as a dynamic referenceframe which can be interconnected with a first 302 that can beinterconnected or positioned relative to the patient 204. Further,various interconnection mechanisms such as connection arms 304 and 306can be interconnected to the first portion of the frame 302 which can bethe base 256. Also a bow or arc 308 can be interconnected with thelinkage arms 304, 306. The tracking sensors 262 a-262 g can allow foreach of the various portions of the stereotactic frame 300 to be trackedwith the navigation system 200. It will also be understood that thevarious linkages such as the linkage arms 304, 306 can be used todetermine the position of the arc 308 relative to the patient 204.

The arc 308 can support a movable element 310 which includes a guidetube 312 provided therewith. The guide tube 312 can allow for passing ormoving of the instrument 252 relative to the patient 204. As discussedabove, the instrument 252 can include a probe, deep brain stimulationelement, implant, etc. Nevertheless, the tracking sensor 262 b can trackthe position of the movable element 310 relative to the patient 204 orthe various tracking sensors 262 a-g can provide more detailedinformation of the position of the guide tube 312 relative to thepatient 204. Nevertheless, the navigation system 200, according to theguided procedure 18, can determine the position of the target,appropriate trajectories, and illustrate the same on the display 130illustrated in FIG. 8, or the displays 225 and 228 (FIG. 9). Thestereotactic frame 300 can then be provided to assist in guiding theinstrument 252 relative to the patient 204. Although the display 130 canalso display the icons illustrating the position of the plannedtrajectory 132 a and the trajectory or current location of theinstrument 252 in icon 132 b, the stereotactic frame 300 can assist inguiding the instrument 252 to the appropriate target. The stereotacticframe 300 can also assist in determining whether the target has beenreached by determining the trajectory of the instrument 252 with theguide tube 312, the distance passed through the guide tool 312, andother appropriate data.

It will be understood that the position of the instrument 252 can beillustrated on the display 130, 225, 228 in any appropriate manner.Although the icon 132 a can include a solid icon 132 b represented orpositioned relative to the planned trajectory 132 a, it can also includea cross-hair 132 c relative to a circle 132 d. The cross-hair canrepresent the position of the instrument 252 and the circle 132 d canrepresent the position or planned trajectory, as illustrated in FIG. 12.Therefore, it will be understood that the display 130, 225, 228 candisplay the information in any appropriate manner.

Also described is an open procedure block 34 that can be assisted withthe guided procedure 18 for various purposes. Although a substantiallyopen procedure in block 34 can generally allow for visualization of thebrain by the physician 282, the guided procedure 18 may assist inhelping the physician 282 to determine the anatomical target and aselected trajectory thereto. Thus, although the guided procedure may notbe guided with a navigated system, the guided procedure 18 can assistthe physician in determining the anatomical target and selecting anentry point, and even assist in selecting a trajectory to reach theanatomical target. Further, the various combinations of the systems canbe provided, so that even a substantially unguided stereotactic framecan be used in the open procedure 34.

The above described methods and algorithms can also be used or executedby the navigation system, including the navigation processor and theplanning processor to determine the anatomical landmarks, the anatomicaltargets, the trajectories, and the like. Also systems like theStimPilot™ system from Medtronic Navigation can be used to performvarious computational and navigational functions. The above-describedsystem can be provided as computer readable or computer executableinstructions to assist a user in using the StimPilot™ system to providefor deep brain stimulation. For example, rather than requiring a user todetermine the AC, PC and the mid-sagittal plane, the above-describedmethod can be loaded onto the work station so that once the image datais appropriately entered into the system, such as merging the imagedata, processing the image data (in addition to that described above),StimPilot™ the system can then determine the anatomical landmarks andfurther determine the location of the anatomical targets, as describedabove. Also, the automatic and manual planning of a system can befurther augmented by the determination of appropriate trajectoriesaccording other method described above. Nevertheless, a system, such asthe StimPilot™ system from Medtronic Navigation, Inc., can be augmentedwith the navigated procedure 18 to assist in achieving a selectedresult.

What is claimed is:
 1. A system to determine an anatomical landmark inan anatomy, comprising: a processor; a first memory system to storeinstructions to be executed by the processor; a second memory system tostore an storing image data of the anatomy; a display operable todisplay the determined anatomical landmark in the image data in theanatomy; and a user input to select a seed datum in the image data;wherein the processor is configured to access the first memory systemand execute instructions stored in the first memory system toautomatically determine the anatomical landmark in the anatomy basedupon the selected seed datum in the image data stored in the secondmemory system, wherein the instructions include: instructions toautomatically segment at least a third ventricle in the image data basedon the selected seed datum; and subsequent to segmenting the thirdventricle, determine at least one of an anterior commissure or aposterior commissure based on the location of the determined thirdventricle in the image data; subsequent to executing the instructions tosegment at least the third ventricle, instructions to automaticallydetermine a location of an anterior commissure in the image datarelative to an anterior portion of the segmented third ventricle by atleast identifying a bright point in the image data at an anteriorboundary of the segmented third ventricle, where the bright pointincludes an intensity change at the edge of the third ventricle and theedge is also the edge of the anterior commissure, subsequent toexecuting the instructions to segment at least the third ventricle,instructions to automatically determine a location of a posteriorcommissure in the image data at a posterior portion of the segmentedthird ventricle at least by identifying a bright point in the image dataat a posterior boundary of the determined third ventricle, where thebright point can be an intensity change at an edge of the thirdventricle that is also an edge of the posterior commissure; andsubsequent to executing the instructions to determine the location ofthe anterior commissure and determine the location of the posteriorcommissure, instructions to automatically locate an anatomical targetthat is relatively indistinguishable from the surrounding structures inthe image data.
 2. The system of claim 1, wherein the user inputincludes at least one of a mouse, a keyboard, a touch screen of thedisplay, or a foot switch.
 3. The system of claim 1, further comprising:an imaging system operable to obtain the image data of the anatomy to bestored in the memory system and processed with the processor.
 4. Thesystem of claim 3, wherein the imaging system includes at least one of amagnetic resonance imaging system, an ultrasound system, a computertomography system, an x-ray system, a positron emission tomographysystem, a planar gamma scintigraphy system, a single photon emissioncomputed tomography system, a multi-slice computed tomography system, orcombinations thereof.
 5. The system of claim 3, further comprising: acommunications system operable to allow communication between theimaging system and at least one of the processor, the memory system, orcombinations thereof; wherein the image data created by the imagingsystem is transmitted to at least one of the memory system, theprocessor, or combinations thereof.
 6. The system of claim 1, furthercomprising: a navigation system operable to track a device relative tothe anatomy; wherein the display is operable to display a position ofthe device superimposed on the image data.
 7. The system of claim 6,further comprising: a device selected from a group including at leastone of a stimulator, a sensor, a probe, a cannula, an ablation device, adeep brain stimulator, a drug delivery device, or a recorder.
 8. Thesystem of claim 7, further comprising a recorder; wherein the recorderis operable to be moved relative to the anatomy; wherein the recorderincludes a recording portion operable to record an activity within theregion of the anatomy; wherein the navigation system is operable todetermine a position of the recording portion relative to the anatomy.9. The system of claim 6, further comprising: a navigation systemselected from at least one of an electromagnetic navigation system, anacoustic navigation system, an optical navigation system, a radiationnavigation system, an accelerometer navigation system, a radarnavigation system, or combinations thereof.
 10. The system of claim 1,further comprising: a navigation frame; a guide portion interconnectedwith the navigation frame; a tracking device coupled to the guideportion; a navigation system operable to determine a position of thetracking device; wherein an icon is operable to be displayed relative tothe image data on the display showing a position of the guide portion.11. The system of claim 1, wherein the seed datum includes at least oneof a user selected portion of the image data, a user selected pixel inthe image data, a bright pixel in the image data, and a pixel in aselected region of the image data.
 12. The system of claim 1, whereinthe instructions further include: at least one of smoothing the imagedata, removing unneeded data in the image data, or combinations thereof.13. The system of claim 1, subsequent to segment at least the thirdventricle in the image data that includes a plurality of slices andprior to determine the location of the anterior commissure or theposterior commissure at an edge of the segmented third ventricle:skeletonize a line in each of the plurality of slices within thesegmented third ventricle; subsequent to skeletonizing the line,determine an axial slope angle and a coronal slope angle of the line;subsequent to determining an axial slope angle and a coronal slope angleof the line, align the plurality of slices in the image data; subsequentto aligning the plurality of slices in the image data, determine amid-sagittal plane based on the skeletonized line in the alignedplurality of slices.
 14. A system to determine an anatomical landmark inan anatomy, comprising: a processor to access image data including atleast a plurality of image slices including a third ventricle andexecute instructions to process the image data; a memory system to storethe instructions to be executed by the processor; a user input toidentify a selected seed portion of the image data; and a display todisplay the processed image data; wherein the processor is operable toautomatically execute the stored instructions configured to: segment athird ventricle in each of the plurality of image slices in the imagedata by growing a region from a selected seed portion based on ahomogeneity method defined in the stored instructions; subsequent tosegmenting the third ventricle in each of the plurality of slices,skeletonize a line in each of the plurality of slices within thesegmented third ventricle; subsequent to skeletonizing the line,determine an axial slope angle and a coronal slope angle of the line;subsequent to determining an axial slope angle and a coronal slope angleof the line, align the plurality of slices in the image data; subsequentto aligning the plurality of slices in the image data, determine amid-sagittal plane based on the skeletonized line in the alignedplurality of slices; and subsequent to aligning the plurality of slicesin the image data, determine a location of at least one of an anteriorcommissure or a posterior commissure at an edge of the segmented thirdventricle; subsequent to determining the location of at least one of ananterior commissure or a posterior commissure at an edge of thesegmented third ventricle, locate an anatomical target that isrelatively indistinguishable from surrounding structures in the imagedata based upon a known location of the anatomical target relative tothe determined at least one of an anterior commissure or a posteriorcommissure; wherein the anatomical landmark is used to determine theanatomical target and the anatomical target is determined for performinga procedure on the anatomical target.
 15. The system of claim 14,further comprising an imaging system operable to create the image dataof the anatomy.
 16. The system of claim 15, wherein the imaging systemincludes at least one of a magnetic resonance imaging system, a computertomography imaging system, an x-ray imaging system, an ultrasoundimaging system, a positron emission tomography system, planar gammascintigraphy system, single photon emission computed tomography system,multi-slice computed tomography system, or combinations thereof.
 17. Thesystem of claim 15, wherein the imaging system is operable to obtainimage data of a brain.
 18. The system of claim 14, wherein the userinputs includes at least one of a computer mouse, a light pen, a touchscreen, or a foot switch.
 19. The system of claim 14, wherein the imagedata includes image data that has been at least one of smoothed,clarified, segmented, aligned, or combinations thereof.
 20. The systemof claim 14, further comprising: a tracking system including alocalizer, a tracking sensor, and a device; wherein the tracking sensoris interconnected with the device to be tracked with the localizer. 21.The system of claim 20, wherein the display is operable to display anicon representing a position of the device relative to the anatomysuperimposed on the image data.
 22. The system of claim 21, furthercomprising: an indication system to assist in defining the anatomicaltarget; wherein the determined anatomical landmark is determined in theimage data and displayed on the display for use with the tracking systemto allow for tracking of the device relative to the determinedanatomical target.
 23. The system of claim 14, wherein the instructionsinclude at least one of smoothing the image data, segmenting the imagedata, identifying portions of the image data, or combinations thereof.24. The system of claim 14, further comprising: a deep brain stimulatorto stimulate a sub-thalamic nucleus of a brain; wherein the anatomicaltarget includes a functional target in the brain that is relativelyindistinguishable relative to surrounding structures including thesub-thalamic nucleus in the brain.
 25. The system of claim 14, whereinthe selected seed portion is identified manually based on severalpossible seed voxels determined and identified in the image data by theprocessor by executing the stored instructions.
 26. The system of claim14, wherein determine the location of at least one of an anteriorcommissure or a posterior commissure at an edge of the segmented thirdventricle includes: determine a location of an anterior commissure inthe image data relative to an anterior portion of the segmented thirdventricle by at least identifying a bright point in the image data at ananterior boundary of the segmented third ventricle, where the brightpoint includes an intensity change at the edge of third ventricle andthe edge is also the edge of the anterior commissure, determine alocation of a posterior commissure in the image data at a posteriorportion of the segmented third ventricle at least by identifying abright point in the image data at a posterior boundary of the determinedthird ventricle, where the bright point can be an intensity change at anedge of the third ventricle that is also an edge of the posteriorcommissure.
 27. A system to determine an anatomical landmark in ananatomy, comprising: an imaging system operable to obtain a plurality ofslices of image data of a brain of the anatomy at least including athird ventricle; a processor operable to execute instructions configuredto automatically: generate refined image data by at least one of smooththe image data, remove unneeded data from the image data, define edgesin the image data, or combinations thereof in each of the plurality ofslices; subsequent to the generate the refined image data, segment thethird ventricle in each of at least a sub-plurality of the plurality ofslices of the generated refined image data of the brain; subsequent tosegmenting the third ventricle, skeletonize a line within the segmentedthird ventricle in each of the sub-plurality of slices in the generatedrefined image data; subsequent to the skeletonize the line, determine aslope of the skeletonized line in at least each of the sub-plurality ofslices in the generated refined image data; subsequent to the determinethe slope, align at least each of the sub-plurality of slices of thegenerated refined image data based upon the determined slope of theskeletonized line in at least each of the sub-plurality of slices in thegenerated refined image data; and subsequent to the align at least eachof the sub-plurality of slices of the generated refined image datadetermine a second region in the aligned image data that defines asecond region of the brain, wherein the second region includes theanatomical landmark that is operable to be used to determine ananatomical target that is relatively indistinguishable from otherstructures in the image data; and a display operable to display at leastone of the first region, the second region, or combinations thereof. 28.The system of claim 27, further comprising: a sensing device including aportion operable to sense a response of the brain.
 29. The system ofclaim 28, further comprising: a communication system operable tointerconnect the processor and the sensing device; wherein the processoris operable to receive the sensed response of the brain to assist indetermining at least one of the third ventricle of the brain, the secondregion of the brain, or combinations thereof.
 30. The system of claim29, wherein the display is operable to display the sensed response ofthe sensing device, the determined third ventricle in the brain, thedetermined second region in the brain, or combinations thereof.
 31. Thesystem of claim 28, wherein the imaging system includes at least one aT1 weighted magnetic resonance imaging system or a T2 weighted magneticresonance imaging system.
 32. The system of claim 31, furthercomprising: a tracking system including at least one of a localizer or atracking device; wherein the tracking device is interconnected with thesensing device so that the tracking system is operable to determine aposition of the sensing device relative to the region in the anatomy.33. The system of claim 32, further comprising: a tracking devicecommunications system wherein the tracking device communications systemis operable to transmit to the processor a tracked position of thesensing device; wherein the display is operable to display an iconsuperimposed on the image data of a position of the sensing devicerelative to the anatomy.
 34. The system of claim 33, further comprising:a user input wherein a user is operable to indicate to the processor aportion of the image data based at least in part on the determined thirdventricle, the determined second region, the tracked position of thesensing device, or combinations thereof.
 35. The system of claim 34,further comprising: a human readable planning display; and a planningprocessor operable to output a plan to reach at least one of the thirdventricle, the second region, determined an anatomical target, orcombinations thereof; wherein the plan is operable to be displayed onthe human readable planning display.
 36. The system of claim 35, furthercomprising: a surgical instrument; a surgical instrument trackingdevice; wherein the tracking system is operable to track the surgicalinstrument tracking device to track a position of the surgicalinstrument relative to the anatomy to achieve the plan.
 37. The systemof claim 36, wherein the surgical instrument includes a deep brainstimulator operable to stimulate a portion of the brain.
 38. The systemof claim 37, wherein the plan includes a trajectory of the deep brainstimulator to reach the determined anatomical target that is afunctional region of the brain that is relatively indistinguishablerelative to surrounding structures, including the sub-thalamic nucleusin the brain.
 39. The system of claim 38, wherein the second regionincludes both an anterior commissure and a posterior commissure, whereindetermine the location of at least one of an anterior commissure or aposterior commissure at an edge of the segmented third ventricleincludes: determine the anterior commissure as a transition in intensityat an anterior edge of the segmented third ventricle and determine theposterior commissure as a transition in intensity at a posterior edge ofthe segmented third ventricle; wherein the trajectory is selected from aplurality of trajectories output by the planning processor, where thetrajectories are determined to the sub-thalamic nucleus based onexecuting the instructions to automatically identify a location of thesub-thalamic nucleus relative to the determined anterior commissure andthe determined posterior commissure.
 40. The system of claim 27, whereinthe imaging system includes at least one of a magnetic resonance imagingsystem, a computer tomography imaging system, an x-ray imaging system,an ultrasound imaging system, a positron emission tomography system,planar gamma scintigraphy system, single photon emission computedtomography system, multi-slice computed tomography system, orcombinations thereof.